In order to provide furnaces with a high capacity, tunnel furnaces or continuous furnaces are used. A continuous furnace is a continuously operating furnaces in which the material, e.g. a metal material, to be heated is fed into the furnace at an inlet, then passes through the furnace heating section and is finally removed through an outlet.
Typically, a continuous furnace comprises several heating sections which are arranged one after another along a transportation direction of the material to be heated. For example, a continuous furnace comprises a pre-heating zone, a firing zone and a cooling zone which are arranged one after another along the transport direction of the material.
In order to transport the material through the continuous furnace, the material is supported onto furnace rollers, or other means along which the material rolls along the transport direction. Specifically, the rollers are driven, e.g. by a driving belt, in order to transport the material along the transport direction through the furnace.
For heating the material within a heating zone, a heating gas or process gas is injected into the respective heating zone. Due to the design of the continuous furnace, i.e. the inlet and outlet openings, it is complex to isolate the heating gas from an environment of the furnace. Hence, an accurate temperature control of a continuous furnace, as well as an energy efficient continuous furnace, is desired.